Impact of fertilizer proportion and fertilizer-water ratio on clogging of filter by fertilizer pump in microirrigation

Fertilization uniformity is an important index to evaluate the performance of the micro irrigation system and understanding the hydraulic performance of water treatment equipment in drip irrigation system is a prerequisite to ensure the stable operation of the system. For the popularization and application of water and fertilizer development of drip irrigation technology, we carried out a test to investigate the effect of fertilization proportion and fertilization-water ratio on clogging of filter by fertilizer pump in microirrigation system. The pump selected was commonly used 120 mesh (diameter 0.13 μm) screen type and disc filter. The test was carried out in the Key Laboratory of Arid Agricultural Water and Soil Engineering of Ministry of education, the Northwest A&F University. The fertilization proportion was 2%, 3% and 4%. The inhaled fertilizer and water ratio was 1:4, 1:5 and 1:6. Water samples were collected to determine the fertilizer concentration at fertilization pump outlet. The concentration of phosphate was determined by an ion conductivity instrument. The uniformity of fertilizer concentration at outlet was assessed by Christensen coefficient, distribution uniformity and statistical uniformity. The results showed that the fertilizer concentration at outlet was different significantly among the 9 treatments. It increased with the increase of fertilizer proportion and inhaled fertilizer and water ratio. At the fertilizer proportion of 4%, the Christensen coefficient significantly differed among the treatments of fertilizer and water ratio. No significant difference was found for the Christensen coefficient at the fertilizer proportion of 2% and 3%. Thus, the high fertilizer proportion could greatly affect the fertilizer concentration uniformity at outlet and we do not recommend the high fertilizer proportion. The water head loss of screen filter became stable at about 3 min for the treatment of the fertilizer concentration equalling to or higher than 0.117%. When the concentration smaller than 0.117%, the water head loss was less than 0.5 m for the screen filter. For the disc filter, the water head loss increased slowly when the fertilizer concentration at outlet was not smaller than 0.067%. But, when the fertilizer concentration at outlet was smaller than 0.067% the water head loss was less than 0.5 m. To avoid filter clogging at a short time, the fertilizer concentration at outlet smaller than 0.117% and 0.067% was recommended respectively for the screen filter and the disc filter. The range of water head loss for the screen filter (0.09-7.75 m) was higher than that for the disc filter (0.32-3.88 m). With the increase of fertilizer concentration at outlet the surface attachment weight was not significantly different for the screen filter but significantly different for the disc filter. The max surface attachment weight was as 11.4 times as the min one. The flow rate of the screen filter decreased from 0.4 m3/h to 0.2 m3/h when the fertilizer concentration at outlet was the highest (0.296%). The flow rate of the disc filter decreased from 0.4 m3/h to 0.3 m3/h when the surface attachment weight increased to 4.56 g. The anti-clogging performance of disc filter was much better than the screen filter when the maximum average fertilizer concentration at outlet was 0.296%. The research can provide the technique support for the popularization and application of integrated water and fertilization technology of drip irrigation equipment. © 2017, Editorial Department of the Transactions of the Chinese Society of Agricultural Engineering. All right reserved.